Australian amateur astronomer Terry Lovejoy has just discovered his third comet. This one’s extra special, because it’s the first member of the Kreutz sungrazing family of comets discovered from Earth in over 40 years. This group of comets, named for German astronomer Heinrich Kreutz, are all believed to be fragments of a much larger comet that broke into pieces centuries ago. The fragments – most of them very small – continue along the old comet’s original orbit and flare into brilliance when they draw near the sun.
Sungrazers aren’t uncommon – every few days one swims through the field of view of the coronagraph on the orbiting Solar and Heliospheric Observatory (SOHO), often brightening from invisibility to the equal of Mercury or Venus as the sun boils them into brilliance. Most vaporize in the heat of the sun’s atmosphere and are never seen again.
Sungrazers are rarely visible from the ground because they’re intrinsically small and faint and only flare up when too close to the sun to be seen. All the glare caused by our atmosphere gets in the way except when viewed in airless space from the SOHO and STEREO probes.
That’s what makes Lovejoy’s discovery remarkable. He found a sungrazer using a camera on his wide-field 8-inch Schmidt-Cassegrain telescope from his home in Brisbane, Australia. Prior to this discovery, Lovejoy discovered several other sungrazers through careful examination of online SOHO photographs. The last sun-approaching comet discovered and seen by a human with a telescope on Earth was Comet White-Ortiz-Bolelli in 1970. It grew a beautiful tail and dazzled at 1st magnitude. I should also mention Comet C/2008 O1 SOHO, originally picked up by SOHO, was captured in a photograph of the August 1, 2008 total solar eclipse.
Lovejoy found his latest comet on November 27 after taking three images each of some 200 different star fields. Studying the pictures, Terry spotted a fast-moving fuzzy object on one of the frames he thought might be just an internal reflection within the camera lens or eyepiece. He returned two mornings later, re-photographing the place he suspected the comet might be and found the ‘fuzz’ again. At that point he requested confirmation from other comet observers, and on December 1 received an e-mail from a team at Mt. John Observatory in New Zealand that they had photographed it, too. Bingo!
Comet Lovejoy is presently 54 million miles from the sun but will sweep only 550,000 miles above its surface when it reaches perihelion or closest approach on Dec. 15-16. Unfortunately, the comet won’t be seen from the northern hemisphere as it speeds through the constellations Lupus, Norma and Scorpius. From the southern hemisphere it’s only about 11th magnitude at the moment and low in the morning sky.
That will soon change. According to the discovery bulletin from the IAU Minor Planet Center, Lovejoy will brighten rapidly in the coming days and reach naked eye visibility by mid-month. Don’t get TOO excited. No one is likely to see it that bright at least from the ground because the comet will be too close to the sun at that time.
Not to fret. Comet Lovejoy will enter the field of view of SOHO’s coronagraph and STEREO’s cameras around Dec. 12. We’ll all have front row, computer-screen seats to watch the spectacle unfold before the comet almost certainly burns up in the sun’s heat near perihelion.
Congratulations Terry on your excellent discovery!